module03-ipaddrV3

module03-ipaddrV3 - IP Addressing Introductory material. An...

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IP Addressing Introductory material. An entire module devoted to IP addresses.
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IP Addresses Structure of an IP address Classful IP addresses Limitations and problems with classful IP addresses Subnetting CIDR IP Version 6 addresses
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IP Addresses Application data TCP Header Ethernet Header Ethernet Trailer Ethernet frame IP Header version (4 bits) header length Type of Service/TOS (8 bits) Total Length (in bytes) (16 bits) Identification (16 bits) flags (3 bits) Fragment Offset (13 bits) Source IP address (32 bits) Destination IP address (32 bits) TTL Time-to-Live (8 bits) Protocol (8 bits) Header Checksum (16 bits) 32 bits
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IP Addresses Application data TCP Header Ethernet Header Ethernet Trailer Ethernet frame IP Header 0x4 0x5 0x00 44 10 9d08 010 2 0000000000000 2 128.143.137.144 128.143.71.21 128 10 0x06 8bff 32 bits
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What is an IP Address? An IP address is a unique global address for a network interface Exceptions: Dynamically assigned IP addresses ( DHCP, Lab 7) IP addresses in private networks ( NAT, Lab 7) An IP address: - is a 32 bit long identifier - encodes a network number ( network prefix ) and a host number
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The network prefix identifies a network and the host number identifies a specific host (actually, interface on the network). How do we know how long the network prefix is? Before 1993: The network prefix is implicitly defined (see class-based addressing ) or After 1993: The network prefix is indicated by a netmask. Network prefix and host number network prefix network prefix host number host number
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Dotted Decimal Notation IP addresses are written in a so-called dotted decimal notation Each byte is identified by a decimal number in the range [0. .255]: Example: 10001111 10000000 10001001 10010000 1 st Byte = 128 2 nd Byte = 143 3 rd Byte = 137 4 th Byte = 144 128.143.137.144
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Example : ellington.cs.virginia.edu Network address is: 128.143.0.0 (or 128.143) Host number is: 137.144 Netmask is: 255.255.0.0 (or ffff0000) Prefix or CIDR notation: 128.143.137.144/16 » Network prefix is 16 bits long Example 128.143 128.143 137.144 137.144
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Special IP Addresses Reserved or (by convention) special addresses: Loopback interfaces all addresses 127.0.0.1-127.255.255.255 are reserved for loopback interfaces Most systems use 127.0.0.1 as loopback address loopback interface is associated with name “localhost” IP address of a network Host number is set to all zeros, e.g., 128.143. 0.0 Broadcast address Host number is all ones, e.g., 128.143. 255.255 Broadcast goes to all hosts on the network Often ignored due to security concerns Test / Experimental addresses Certain address ranges are reserved for “experimental use”. Packets should get dropped if they contain this destination address (see RFC 1918): 10.0.0.0 - 10.255.255.255 172.16.0.0 - 172.31.255.255 192.168.0.0 - 192.168.255.255 Convention (but not a reserved address) Default gateway has host number set to ‘1’, e.g., e.g., 192.0.1. 1
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Subnetting Subnetting Problem : Organizations have multiple networks which are independently managed Solution 1: Allocate a separate network address for each network Difficult to manage From the outside of the organization, each network must be addressable.
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module03-ipaddrV3 - IP Addressing Introductory material. An...

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